Noneffect of electronegative gases on pulsed laser-induced optical surface damage thresholds

Laser-induced damage testing was conducted on a variety of optical surfaces using an Nd:YAG laser. The samples tested included conventional dielectric coatings of ZrO2, diamond-turned copper, bare surfaces of fused silica and ARG-2 glass, and porous surface layers of both leached ARG-2 glass and some solgel coatings. Measurements were made in vacuum and in nitrogen, Freon 14 (CF4), and SF6 at pressures up to 2 atm. It is found that the ambient gas has no observable effect on the surface damage threshold, in agreement with previous observations that damage sites are initiated on or just below the surface of optical elements.